zimu's recommendation about meditation is what i would suggest. it sounds like you're storing tension in your body and mind when trying to fall asleep.
try this to release tension in your body:
lying prone in bed, concentrate on your breathing. imagine the air actually travelling in through your nose, down your throat, into your lungs, and then back out. after doing this for about a minute take one deep breath as big as you can, hold for a few seconds then explosively(not too explosively, but more like forcefully) release it.
breathe relaxed for about a minute then take in another deep breath but this time start contracting all the muscles in your body at the same time(it sounds difficult to do but it's ok if you don't get all of them, it's better that you at least try to) and at your full lung capacity, hold the breath and contract your muscles as hard as you can, then explosively release both the breath and your muscles. then go back to relaxed breathing.
now doing relaxed breathing, start at your feet and try to think about every last detail about them and concentrate on actually releasing any tension built up there and after about a minute, take in a deep breath and start to contract all the muscles in your feet, contracting them more as you approach your fullest lung capacity. when you reach maximum lung capacity, contract your feet muscles as hard as you can, and hold that breath for a few seconds then explosively release both the air and your feet muscles. then go back to relaxed breathing.
repeat the preceding paragraph for all body parts(calves, thigh, pelvis, stomach, back, arms, face/neck).
after the last body part, do one final deep breath and this time contract your entire body's muscles again and hold that breath as you contract as hard as possible and then explosively release again after a few seconds. then continue with relaxed breathing.
this should help release the tension in your muscles.